JPS5975115A - Flow rate detector - Google Patents

Abstract

PURPOSE:To improve responsibility and to obtain small-sized, lightweight constitution by providing a diaphragm constituted so that one surface receives the total pressure of fluid increased in velocity by a flow velocity increasing means and the other surface receives the static pressure of the fluid. CONSTITUTION:The diaphragm 11 constituted so that one surface receives the total pressure of the fluid increaseded in velocity by the flow velocity increasing means 20 and the other surface receives the static pressure of the fluid is provided in piping 19. The diaphragm 11 deforms according to the amount the static pressure 1/2XPU<2>, where R is the density and U is the flow velocity. This deformation is transduced into the impedance of a strain detecting element 9 and the impedance is amplified through a differential amplifier to obtain a detection output signal. Therefore, when the density rho of the fluid is known, the flow rate Q is found from the flow velocity U by the parallel processing of an analog correcting circuit or by the squaring arithmetic of a microprocessor through an A/D converter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate detection device that measures the flow rate of a flowing fluid based on the amount of pressure deformation of a diaphragm.

A conventional device of this type is shown in FIG. In the figure, (1) is a bulk heating element made of silicon semiconductor, (2) is an electrode lead that supplies power to the heating element (1) and also serves as support, and (3) is a transistor that holds the electrode lead (2).・Support corresponding to the package, (4) is the extraction lead, (5) is the stainless steel piping,
(6) indicates the flow direction of mineral oil, which is a fluid passing through the inside of the pipe (5). (7) is a detection circuit including a differential bridge and an amplifier, and (8) is a detection output signal.

Next, the operation will be explained. Heat generation (4, (1) - 1 power supply is Pin and heat transfer amount between heating element (1) and mineral oil is Pout. In thermal equilibrium state, Pin = Po
ut = h・As・ΔT holds true. Here, h is the heat transfer coefficient between the heating element (1) and mineral oil, and As is the heating element (1)
surface area, ΔT is the temperature difference between the heating element (1) and the mineral oil. In general, the Reynolds number Re is 1 (2000
Under laminar fluid conditions, the heat transfer coefficient can be approximated by the experimental formula h=n+b-U'·5, where a and h are constants. Here, V means the average flow velocity of the fluid. The power supply Pin to the heating element (1) is determined by the resistance of the heating element (1) being Rs, Q
Is the flow.

If the voltage is Vs, then Pin = l52- Rs =
By measuring the electrical impedance of the heat generating element (1) expressed by Vs2/]Rs with the detection circuit (7), the flow velocity (2) or the flow ff1Q is obtained as a detection output signal (8). Heating element (1) is 0.7X O, 7X
O,15- silicon chip, P is 1015C++
+ Consists of doped N-type homogeneous material. The support (3) is a TO-46) transistor package, and the stainless steel pipe (5) is
7671 diameter x 30 pieces long 1 heating element (1) is 25.
It is installed at 8ff.

Since the conventional heat-sensitive flow rate detection device is constructed as shown below, the Reynolds number is 2,000 to 8,000.

In order to avoid the transition region from laminar to turbulent flow where the flow becomes unstable, the Reynolds number is set to 2000 or less, and the heat transfer coefficient is set to a low value, and the grain is set to I have no choice but to use flow state.

Furthermore, since the silicon chip serving as the heating element (1) is a homogeneous bulk heating element, the heat capacity is large and the thermal time constant for reaching a thermal equilibrium state is also relatively large. In addition, the heating element 9 (1) has a certain size, and together with the electrode lead (2), it becomes an external element that disturbs the flow, which not only lowers the responsiveness of the flow rate detection device, but also makes it difficult to detect minute flow rates or It had unstable characteristics at large flow rates.

This invention was made in order to eliminate the drawbacks of the conventional ones such as L, and includes a flow rate increasing means for increasing the flow rate of the fluid, and one surface of the present invention has a total flow rate of the fluid whose flow rate is increased by the means. a diaphragm whose other surface is configured to receive the static pressure of the L fluid and deforms under pressure due to the dynamic pressure of the L fluid, and a means for detecting distortion of the diaphragm; An object of the present invention is to provide a flow rate detection device capable of instantaneously measuring the flow rate by providing a support member having a means for supporting and introducing static pressure of the fluid T in a pipe through which the fluid L passes. There is.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, (9) is a strain detection element consisting of a buried P-type silicon impurity diffusion layer and serving as a strain detection means; 00
is an insulating layer made of an 8i02 oxide film formed by thermal oxidation, αυ is a pressure-receiving diaphragm made of an N-type silicon substrate whose central part, where the strain sensing element (9) is arranged, has been etched and thinned; (1) b) is the peripheral edge of this diaphragm 0υ, @ is the aluminum electrode layer.

03 is a bonding wire, 0 is a bonding post, and OQ is an adhesive layer made of glass solder.

The support is composed of a support (16a) made of a silicon substrate and having an introduction hole I2υ which is a means for introducing static pressure of fluid, and a support (46b) made of silicate glass. 07) is an insulator made of a monolithic insulating material such as ceramic or synthetic resin, which insulates and supports the bonding post O4, θ is a package made of Kovar, OQ is a housing, and a wire is used to increase the flow velocity of fluid such as mineral oil. This is a nozzle that is a means of increasing the flow velocity to increase the flow rate. The pressure-receiving diaphragm 0 (g) is not limited to silicon, but can be made of silicon, Ge or In5b if it is a semiconductor piezoresistive material.
, or a compound semiconductor such as GaAs. Insulating layer OQ
As for 8i0□ pond Si3N4. Any electrically insulating material such as Al2O3 may be used. Adhesive layer (
+71 is ZnO-B203-V2O, which has a coefficient of thermal expansion close to that of silicon, so that it can be hermetically sealed at a relatively low temperature.

Although glass solder based on this type is used, alloys such as aAu-Si, or synthetic resin adhesives such as epoxy and silicone may also be used. It should be selected according to the operating temperature range and the fluid to which it will be used as a flow rate detection device, and should be chemically and physically stable with respect to the fluid to which it is applied, such as insolubility, and can be used in a wide operating temperature range. In contrast, it is preferable to use a heat-resistant adhesive having a coefficient of thermal expansion at least close to that of the pressure-receiving diaphragm α. Support (16R), (t6
For b), due to residual thermal stress and its temperature dependence, it is necessary to match the thermal expansion coefficient with the pressure receiving diaphragm 0υ, but it is not limited to silicon materials or silicate glass as long as the thermal expansion coefficient is similar. It may also be a porcelain ceramic material such as Zonoike glass material, 'f2, copierite, zircon, or lithia. Although mineral oil is used as the fluid, it is not limited to this, and fuel oils such as gasoline and kerosene, as well as water and air can be used.

Applicable to most fluids such as city gas and N2.

Particularly suitable for insulating fluids.

Non-insulating fluids can also be used with electrodes (2) and bonding wires 03. This method can be sufficiently applied by coating the bonding post 0→ with an insulating film.

Next, the operation will be explained. The mineral oil is accelerated by the nozzle (E), becomes a jet, and collides with the pressure receiving diaphragm αυ. A total pressure, which is the sum of the dynamic pressure and static pressure of the mineral oil, is applied to the surface of the pressure receiving diaphragm 0υ that collides with the jet stream. On the other hand, static pressure is applied to the opposite surface of the pressure receiving diaphragm αη via the introduction hole Q]). The pressure receiving diaphragm 01) deforms according to the dynamic pressure 1'OU2, where ρ is the density and U is the flow velocity. This deformation is converted into the impedance of the distortion detection element (9) having a full bridge configuration, and is amplified through a differential amplifier to become a detection output signal. This type of detection method is often adopted in known semiconductor diffusion pressure detectors, and has linear conversion characteristics, so the amount of dynamic pressure i
ρU2 will be directly measured. Therefore.

If the density p of the fluid is known, the flow rate Q can be determined from the flow rate U by performing squaring with an analog correction circuit or by performing squaring with a microprocessor through a ψ converter. If the density ρ of the fluid is unknown, the flow rate can be determined by separately installing a density detector, performing division processing, and then taking the square. Supports (16a) and (16b
) The coefficient of thermal expansion is slightly different between the two, which will generate thermal stress, but the support (16B) absorbs a considerable portion of the thermal stress and has almost no effect on the pressure receiving diaphragm αη. It looks like this. In this way, the support (
16a) plays not only the role of introducing static pressure but also the role of improving temperature dependence due to thermal stress, and it is significant that it is made of the same material as the pressure receiving diaphragm 01) as in this embodiment. Support body (16a) and support body (16b
) The total energy of thermal stress is also suppressed by reducing the bonding area between the two.

The flow near the pressure receiving diaphragm (0]) is set in a turbulent region with a Reynolds number of 8000 or more by the nozzle), and the turbulent state is always maintained within the measured flow rate range, and it never enters the transition region between 1-flow and turbulent flow. stable output can be obtained. After the flow of mineral oil (6) collides with the pressure receiving diaphragm 0υ, it is bent 90 degrees and discharged, and has the advantage of being much smaller and lighter than conventional ones. In addition, due to the impact energy of the jet and the vortices generated near 0υ of the pressure-receiving diaphragm, it is difficult for dirt and deposits to adhere to the pond, and the characteristics do not change over time and are excellent in durability.
As shown in the figure, this detector is easy to install and replace. Since it uses semiconductor materials, it is excellent in mass production and can be produced at low cost and with much higher performance. Although an N-type silicon substrate has been described here, the same can be realized for a P-type silicon substrate as well.

FIG. 8 shows an embodiment of the pond according to the present invention, in which there is one support (16b), and the support (16b) has an introduction hole Q.
υ is perforated.

Although the influence of thermal stress is greater than that shown in Fig. 2, it is possible to realize a smaller product at a lower cost since the manufacturing process is reduced. In this way, the introduction hole Qη may be provided in a part of the pressure receiving diaphragm α as long as it has a structure that introduces static pressure to the back surface of the pressure receiving diaphragm 0η.

FIG. 4 shows an embodiment of the present invention, in which a strain detection element (9) is stacked on a pressure receiving diaphragm αυt.

The inlet Qυ of the static pressure of the fluid is connected to the pressure receiving diaphragm αη.
This figure shows the case where it is provided directly at the peripheral edge (nb), which is thicker than the center. In this case, the peripheral edge of the diaphragm (
11h) may also be considered as part of the support.

The strain detection element (9) is a known resistance wire strain gauge or semiconductor strain gauge. The pressure receiving diaphragm (II) is made of a metal material such as stainless steel, which is an elastic material capable of forming a membrane body, or a semiconductor such as silicon. 00 is an insulation 1- which covers the entire surface or a part of this pressure receiving diaphragm 0◇ and is made of an electrically insulating material.

The material of the insulating layer 01 may be a metal oxide film, a heat-resistant monomolecular film, or IHA840, 8iQ, MgF2. CaF
2. This may be a vapor-deposited thin film such as Zn8.

Basically, the movement is the 8th. There is no difference from Figure 4.

If a semiconductor is not used, the temperature dependence can be reduced, which is advantageous when used over a wide range or for high-temperature fluids. Since the strain sensing element (9) is directly exposed to the fluid, the strain sensing element (9), electrode layer (6), bonding wire (to), bonding post 04, etc. are coated with the same material as the insulating layer OQ. is desirable. Further, by providing the static pressure inlet 01) directly on the peripheral edge of the pressure receiving diaphragm 0η, the number of manufacturing steps is reduced and manufacturing becomes easier.

Figure 5 shows an embodiment of the pond of this invention, in which a temperature detection element (A) for temperature compensation is installed at the pressure receiving diaphragm = (+1>).This temperature detection element (A) is made of silicon. This is an impurity diffusion layer formed within the pressure receiving diaphragm αυ made of a substrate, and is arranged at the peripheral edge of the pressure receiving diaphragm Op so as not to receive the deformation stress of the pressure receiving diaphragm 0υ.

In general, electrical resistivity is determined by the product of charge carrier concentration and mobility, but in semiconductor materials such as silicon, the value of both changes significantly with temperature even at room temperature, and strain detection Rokuko (9) temperature dependence is often a problem. For example, when measuring flow rate over a wide temperature range, such as in automobile applications, it is necessary to provide a temperature compensation element separately from this embodiment. In other words, it is necessary to remove only the temperature-related term from the electrical impedance change of the strain sensing element (Q) to extract only the deformation stress term due to the piezo effect. As in this embodiment, a temperature detection element (A) made of, for example, a temperature-sensitive resistance material is placed in a portion where deformation stress is not applied, and a differential amplifier tube is used. By amplifying the detection circuit included, it is possible to perform measurements over a wide temperature range. In addition, forming such a temperature detection element (a) can be easily realized by simply using different mask patterns, with little impact on cost. The temperature detection element (a) is an impurity diffusion layer of silicon material.

Such as thermistors! It may also be constructed using a temperature-sensitive semiconductor or the like.

FIG. 6 shows another embodiment of the present invention, in which the nozzle (20a)
.

(20b), pressure receiving da (-? 7 la A (ll&),
(llb), Ni detection element (not shown), support (
16a), (x6b), etc.+C, J: This shows a case where the flow rate detection devices configured as shown in FIG. Although not shown, it is desirable to also provide temperature detection means for temperature compensation. In the figure, @ is an O-ring for sealing, (c) is a circuit board for mounting electronic components that make up the detection amount f, and @ is a nozzle (20a), (2
0b) A discharge hole for discharging the injected mineral oil (6) from the bonding post Q4 to the circuit board (c)
As shown in Figure 7, the nozzles (20a) and (2ob) are integrated with the package (to).

The aperture diameter is different. The discharge hole (c) was also drilled in the package (to), and the piping was arranged in series and had a similar configuration. 1 by two flow rate detection devices
It consists of two flow rate detection devices. In this embodiment, since the orifice diameters of the nozzle (20a) and the nozzle (2ob) are different, the flow rate when detecting a change in the phase state, such as the inclusion of air bubbles, is also controlled by the two flow rate detection devices shown in L. It can be found by comparing the outputs of That is,
True mass flow rate measurement can be achieved by arranging multiple flow rate detection devices that are based on the same dynamic pressure measurement principle but have different functional relationships in series or parallel as one unit or in a similar state. can. In addition, even if one of the flow rate detection parts is damaged, it is possible to measure the flow rate with temperature correction. It can be operated without stopping the operation. In addition, in this example, the nozzles (20a) and (20b)
By changing the diameter of the orifice, the amount of dynamic pressure generated by the plurality of flow rate increasing means is made to have a different functional relationship with the flow velocity of the fluid. It is also possible to use a similar method in which the intervals are different.

In addition, in the described embodiment, a nozzle (A) is used as a flow rate increasing means.
Although the case is shown in which an orifice, a vent, etc. are used, it is also possible.

In addition, 2.l: In the example described above, the support (16a), (t
6b) was constructed from a silicon substrate or silicate glass.

A similar effect can be obtained by using a porous material.

In addition, in Example 1, supports (16a) and (16b
) has been made into an integral structure, but it is also possible to arrange a plurality of supports geometrically symmetrically, for example, on the same circumference t, and to support the diaphragm Ql) on those t. According to the invention, there is provided a flow rate increasing means for increasing the flow rate of the fluid, and one surface has a total pressure of the fluid whose flow rate is increased by the means.

A diaphragm whose other surface is configured to receive the static pressure of the h fluid and is deformed by the dynamic pressure of the t fluid, and means for detecting distortion of the diaphragm.

A support body supporting the periphery of the diaphragm and having a means for introducing static pressure of the fluid t is provided in the piping through which the fluid t passes, resulting in an extremely small and lightweight design with excellent responsiveness. This has the effect of providing a high-performance flow rate detection device at a low cost.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the inside of a conventional flow rate detection device with a portion cut away, FIG. 2 is a sectional view showing a flow rate detection device according to an embodiment of the present invention, and FIGS. FIG. 7 is a sectional view showing a flow rate detection device according to another embodiment. In the figure, (9) is the strain detection means, αη is the diaphragm, (11b) is the periphery of diaphragm A (7), (l
sa), (16b) i is the support, 0* is the piping,
elJ, (20a) and (20b) are flow velocity increasing means, C1) is means for introducing static pressure of fluid, and C1) is temperature detecting means. Note that the same line numbers in each figure indicate the same or corresponding parts. Figure 6 Procedural amendment 2, name of invention Flow rate detection device 3, relationship with the case of the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Representative of Mitsubishi Electric Corporation Person: Jin Hachibe 4, Katayama, Agent Address: 2-3 Marunouchi 2-chome, Chiyo 11-ku, Tokyo
So Mitsubishi Electric Co., Ltd. +]i+1゜2. 5. Scope of Claims and Detailed Description of the Invention in the Specification Subject to Amendment Column 6, Contents of the Amendment (1) The scope of claims in the Specification will be corrected as shown in the attached sheet. (2) Specification "Under laminar fluid conditions" on page 4, line 12 of the book is corrected to "laminar flow conditions." (3) Correct “h=a+b −U J” in line 14 of page 4 to “h=a+b−VJ.” (4) Correct “grain” to “flow” in line 12 of page 5. do. (5) On page 5, line 20, "indeterminate" is corrected to "unstable." (6) Change “In5b” on page 7, line 14 to “InSb”
Correct to J. (7) Correct "ora" to "kara" on page 8, line 8. (8) "Accurate" in the second line of page 14 is corrected to "compression." (9) Correct "geometry" in line 14 of page 16 to "geometry". 7. One or more documents stating the scope of claims after the amendment to the list of attached documents Claims (1) Flow rate increasing means for increasing the flow rate of fluid;
A diaphragm having a groove formed so that one surface receives the total pressure of the fluid whose flow velocity has been increased by this means and the other surface receiving the static pressure of the fluid and is deformed by the dynamic pressure of the fluid; A flow rate detection device comprising: a means for detecting distortion of the diaphragm; and a support having means for supporting the peripheral edge of the diaphragm and introducing static pressure of the fluid, in a pipe through which the fluid passes. (2) The flow rate detection device according to claim 1, wherein a semiconductive material is used as the diaphragm that deforms under pressure. (3) The flow rate detection device according to claim 2, wherein a silicon material is used as the diaphragm that deforms under pressure. (4) The flow rate detection device according to any one of claims 1 to 8, characterized in that the diaphragm that deforms under pressure has a structure in which a central portion thereof is thinner than a peripheral portion. (5) Claim 4, characterized in that the diaphragm that deforms under pressure has a tapered structure in which the center portion thereof is thinner than the peripheral portion, and a static pressure introduction hole is provided in the peripheral portion of the diaphragm. The flow rate detection device described. (6) The flow rate detection device according to claim 8, characterized in that a silicon material is used as the support. (7) The flow rate detection device according to any one of claims 1 to 5, characterized in that a porous material is used as the support. (8) Claim 1, characterized in that the support supporting the periphery of the diaphragm is composed of a plurality of supports arranged geometrically symmetrically on the same plane. 6. The flow rate detection device according to any one of items 6 to 6. (9) The flow rate detection device according to any one of claims 1 to 8, characterized in that it has means for detecting temperature for temperature compensation. (10 A plurality of flow rate detection devices each consisting of a flow rate increasing means, a diaphragm, a strain detection element, and a support are arranged in series or in parallel with respect to the flow line direction in a pipe through which the fluid passes, and A flow rate detection device characterized in that the amount of dynamic pressure generated by each of the flow rate increasing means has a different functional relationship with the flow rate of the fluid.O9 A flow rate detection device characterized in that it has a means for detecting temperature for temperature compensation. A flow rate detection device according to claim 10.

Claims (9)

[Claims] (1) a flow rate increasing means for increasing the flow rate of the fluid;
A diaphragm is configured such that one surface receives the total pressure of the fluid whose flow velocity has been increased by this means, and the other surface receives the static pressure of the L fluid, and is deformed by the dynamic pressure of the L fluid. A flow rate detection device comprising: a means for detecting strain; and a support having a means for supporting the periphery of the diaphragm and introducing static pressure of the fluid L, in a pipe through which the fluid t passes. (2) The flow rate detection device according to claim 1, wherein a semiconductive material is used as the diaphragm that deforms under pressure. (3) The flow rate detection device according to claim 2, wherein a silicon material is used as the diaphragm that deforms under pressure. (4) The flow rate detection device k according to any one of claims 1 to 8, characterized in that the central portion of the diaphragm that deforms under pressure is thinner than the peripheral portion. (5) The diaphragm that deforms under pressure has a structure in which the center portion thereof is thinner than the peripheral portion, and a static pressure introduction hole is provided in the peripheral portion of the diaphragm (t). The flow rate detection device described. (6) The flow rate detection device according to claim 8, characterized in that a silicon material is used as the support. (7) The flow rate detection device according to any one of claims 1 to 5, characterized in that a porous material is used as the support. (8) Claim 1, characterized in that the support that supports the periphery of the diaphragm is composed of a plurality of supports that are arranged geometrically symmetrically on the same plane t.
The flow rate detection device according to any one of Items 6 to 6. (9) The flow rate detection device according to any one of claims 1 to 8, characterized in that it has means for detecting temperature for temperature compensation. In the piping through which the 00 fluid passes, there is a flow rate increasing means. A plurality of flow rate detection devices each including a diaphragm, a strain detection element, and a support are arranged in series or in parallel with respect to the flow line direction, and the amount of dynamic pressure generated by the plurality of flow rate increasing means is A flow rate detection device characterized in that it has a different functional relationship with respect to the flow velocity of a fluid indicated by L. 11. The flow rate detection device according to claim 10, further comprising means for detecting the entire temperature for 0υ temperature compensation.